The aim of the study is to determine relevant hemodynamic parameters for the diagnostics of pulmonary arterial hypertension (PAH) by dynamic contrast enhanced dual-energy CT (DE-CT). In this pilot study the investigators investigate patients who underwent right heart catheterisation with DE-CT to determine hemodynamic parameters and control the results by other clinical investigations. The investigators expect that using this non-invasive method, parameters relevant for the diagnosis of the patients with PAH, like pulmonary blood volume, blood flow and perfusion heterogeneity, can be determined.